Essay
Unit 18 Assignment 3 Dihybrid and monohybrid
- Institution
- PEARSON (PEARSON)
This achieved the criteria.
[Show more]
Content preview
GeneticsAssignment 3
P4
Through the process of reproduction each individual produces beings identical to themselves. Reproduction is
generally categorized into two types; asexual and sexual. Some eukaryotes (have cells which have a nucleus
enclosed within their membranes) and all prokaryotes (do not have a nucleus) reproduce through asexual methods
such as; fragmentation, binary fission, etc. Whilst the majority of eukaryotes reproduce through sexual
reproduction whereby two organism’s genetic material combine together to create a new individual this is done
through the process of meiosis. Meiosis is a specialized type of cell division which occurs only in gametes or
specialized sex cells.
Meiosis is a very significant process. For long-term survival of a species it needs the ability to adapt to an ever-
changing environment or the species needs to be able to colonize in other new environments. For species to
achieve this there needs to be a variation in offspring from their parents and from each other, this is known as
genetic variation. Genetic variation is a key factor for biological diversity as it is the essence of evolution. If
amongst individuals there was no genetic differences, then “survival of the fittest” wouldn’t be possible and its
likely everyone would be the same. An increase in genetic variation means a wider variation is susceptibility to
diseases. So, if there was an occurrence of an epidemic of a disease, the variation in the population would prevent
us all from being wiped out. Essentially, genetic variation has infinite possibilities due to sexual reproduction as
sexual reproduction creates offspring which are genetically unique. As the offspring will not only differ from one
another but also both parents. This variation can occur in three ways; Random assortment of chromosomes,
crossing-over of chromosomes, and fusion of haploid gametes.
1. Random Assortment of Chromosomes
Random assortment also known as independent assortment essentially explains how genes which are different are
able to separate from each other during the development of reproductive cells. This process was first explained by
scientist Gregor Mendel (1822-1884) during a study in 1865 of the genetics within dihybrid pea plants. Mendel was
carrying out crosses between organisms with two different traits. Through this he discovered that the combination
of traits within the offspring sometimes didn’t match the combinations of traits within the parental organisms.
From this, he created the principle know as Independent Assortment. Independent assortment is a term used to
describe Independent assortment of genes which takes place in eukaryotes during meiosis, it describes how pairs
of alleles independently separate from one another during the formation of gametes, leading to a larger possibility
in fertilized offspring. Essentially meiosis is a form of cell division which reduces the parents cell number of
chromosomes by half so that four reproductive cells known as gametes are produced. In humans, diploid cells
consist of 46 chromosomes, with 23 chromosomes inherited from the mother whilst the other 23 (similar set) are
inherited from the father, these are known as homologous chromosomes. However, during meiosis these
homologous chromosome pairs are divided into half to create haploid cells, and this assortment separation of
these homologous chromosomes is random. This is through metaphase l whereby the homologous chromosomes
line up at the equator as bivalents in two possible arrangements which are as follows;
Left – maternal copy/ Right- paternal copy
Left- paternal copy/ Right- maternal copy
Each homologous pair orientation is random, this will not be affected by any other homologous pair's orientation.
Essentially, an allele on one chromosome has an equal chance of being separated or paired with any allele present
on another chromosome, their inheritance is initially independent on each other. However, independent
assortment WILL NOT take place if two genes are located on linked genes (the same chromosome.)
There are over 8 million (223) chromosome configurations within humans, in which during meiosis in metaphase l
chromosomes line up. This is a specific process of meiosis, which can create four unique haploid gametes which
can create many combinations. Then independent assortment, whereby the chromosomes inherited from either
1
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller ld2908. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £2.99. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
55628 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now